Sustainable Islanding System Based on Dual Power Inverters with Cooperative Generator

This paper proposes a sustainable islanding system for microgrid which consists of dual power inverters and a cooperative generator. The system can be separated from the utility grid with two islanding operations, one is normal islanding operation that maintains the stable power supply to all loads, the other is protective islanding operation that protects prior part of the load from the power outage even when the grid fault occurs unexpectedly. These operations are based on a multi-mode control of the inverters between the constant current and constant voltage modes, and the cooperation of the local generator that supports enough power to the voltage mode inverter for the successful islanding operation. In addition, the inverters use the voltage synchronization to reconnect to the grid, which makes the mode transition seamlessly. The islanding operations of the proposed system were verified through the simulations using PSIM tool. The power supply to the prior load was continuous by detecting the grid fault in 10 ms and by changing the voltage source from the grid to the inverter. Then, the other inverter and the generator cooperated to supply power to the other load according to the predefined procedure.